Field of the Invention
The present invention relates to a phase-difference detection type focus detection technique.
Description of the Related Art
Japanese Patent Laid-Open Nos. 58-024105 and 2005-106994 disclose techniques for performing focus detection based on image signals obtained by an image capturing unit including pixels, each being pupil divided by a microlens. According to Japanese Patent Laid-Open No. 58-024105, each pupil-divided pixel receives light beams that have passed through different pupil regions of an image forming optical system via the microlens. Also, according to Japanese Patent Laid-Open No. 2005-106994, some of the pixels constituting an image capturing unit include a photoelectric conversion unit divided into two so as to detect a focus state of a lens, and the photoelectric conversion unit receives, via a microlens, light beams that have passed through different pupil regions of the lens.
Japanese Patent Laid-Open No. 2013-072906 discloses a technique in which in phase-difference detection type focus detection, for the purpose of improving the SN ratio, correlation values of a plurality of distance measurement lines are obtained, and the amount of offset between two images is obtained after the correlation values of the plurality of distance measurement lines are added.
In the phase-difference detection type focus detection described above (hereinafter, referred to as “phase difference AF”), determining how much amount of pixel data needs to be read out for calculation processing to perform focus detection is a very important factor in terms of detection accuracy and the speed of processing. In addition, if all pixel data is input, with the image capturing unit including pixels each being divided into two, the amount of data is twice that of captured image, and thus a significantly large load is placed on a processing circuit in a subsequent stage.
For example, measures are required to be taken such as implementing parallel processing and increasing the clock frequency, which generates heat and further requires a thermal solution to be implemented in the mechanism, making it difficult to achieve cost reduction. Accordingly, there is a need for, for example, pixel data for focus detection to be thinned according to a desired detection accuracy, whereas pixel data for an image is generated by adding the data of a pixel divided into two.